1. Technical Field
The present invention relates to a valve driving device that forcibly opens a self-sealing valve (a pressure adjustment valve) that is continuous with a liquid droplet discharging head, a functional liquid supply unit, and a liquid droplet discharging apparatus.
2. Related Art
In the related art, a pressing mechanism, which is incorporated in a valve unit, for adjusting the pressure of an ink to be supplied to a head is known as such a valve driving device (refer to JP-A-2012-111044).
Such a valve unit includes an accommodation chamber formation member in which an ink accommodation chamber is formed. An ink accommodation chamber is provided with a first chamber that is connected to an ink supply mechanism via a supply tube, a second chamber that is connected to a head via a connection flow channel, and a communication portion that is in communication with the first chamber and the second chamber. In addition, an opening portion is formed in the second chamber, and a flexible member is provided in the opening portion so as to block the opening portion. A pressure receiving plate is provided in the central portion of the flexible member, and the flexible member is in a state in which the flexible member is exposed at the peripheral portions of the pressure receiving plate. Furthermore, a valve is provided extending across the first chamber and the second chamber. The valve includes a flange portion having a seal, and a shaft portion, the flange portion is installed in the first chamber, and the shaft portion extends from the flange portion up to the vicinity of the flexible member of the second chamber. In addition, a biasing mechanism for adjustment, which biases toward a direction in which the valve becomes blocked, is provided in the first chamber.
When ink is discharged from the head, the second chamber reaches a negative pressure, and the flexible member deforms on the inner side due to atmospheric pressure. When the flexible member deforms, the shaft portion is pressed, the valve is opened, and ink flows into the second chamber from the first chamber. When ink flows into the second chamber and the negative pressure of the second chamber is reduced, the deformation of the flexible member is reduced, and before long the biasing force of the biasing mechanism increases and the valve is blocked. In this manner, the pressure of ink to be supplied to the head is adjusted.
The pressing mechanism includes an air bag that is installed on the outer side of the flexible member, and an air driving mechanism that is connected to the air bag. When air is supplied to the air bag from the air driving mechanism, the air bag expands and causes the flexible member to deform on the second chamber side. As a result of this, the valve is forcibly opened. On the other hand, when air is removed from the air bag, the air bag contracts, the deformation of the flexible member is canceled, and the valve is blocked by the biasing mechanism.
The opening and closing of the valve by the pressing mechanism is implemented during the implementation of so-called pressurized cleaning of the head. Pressurized cleaning of the head (nozzles) is implemented by forcibly discharging ink from the head as a result of the air bag being expanded (the air driving mechanism being driven) in synchronization with driving of a pressurization mechanism that is connected to the first chamber. In addition, pressurized cleaning is finished by contracting the air bag in synchronization with stopping of the driving the pressurization mechanism.
In such a pressing mechanism (a valve driving device) of the related art, an air bag to be contracted becomes separated from a flexible member in a process that finishes pressurized cleaning. To explain in further detail, in terms of the shape thereof, an air bag becomes separated from a flexible member of the peripheral portions of the pressure receiving plate prior to becoming separated from the pressure receiving plate, and therefore, when the air bag becomes completely separated from the pressure receiving plate, the flexible member (the peripheral portions) slightly deforms on the outer sides. That is, residual pressure is generated in the second chamber in a state in which the air bag is separated from the flexible member. In addition, it takes time to remove air from the air bag, and therefore, the blocking of the valve also takes time.
Accordingly, dripping (oozing out over time) of ink still occurs in the head after pressurized cleaning is finished (driving of a pressurization mechanism is stopped), and therefore, there is a problem in that it is not possible to transition to a subsequent wiping operation of the head (of a nozzle surface) in a short period of time. When time is required between the end of pressurized cleaning and the initiation of wiping, in a case in which the head is facing sideways such as horizontally, a gravitational force acts upon the ink that oozes out, the state of the nozzles of the head changes, and therefore, effective wiping is not possible.